如果您的接口带有对象集合，并且既需要该接口的只读版本又需要该接口的读写版本，该怎么办？

Question

I'm currently creating some interfaces for user controls that will contain collections of objects. I want to have an interface for a control that can have objects added from the outside, and another interface for one that cannot have objects added from the outside. So far I basically have the following (simplified for this question; if it would help you to see the actual code I have thus far please let me know):

public interface IReadableFoo 
{
    IReadOnlyCollection<Foo> Foos { get; }
}

public interface IReadWriteFoo : IReadOnlyFoo 
{
    new ICollection<Foo> Foos { get; }
}

What is considered the "best practice" to do in this situation where you have an interface with a collection of objects, and you want to have both a read-only version and a read-write version? Is it considered acceptable to have an ICollection<Foo> shadowing an IReadOnlyCollection<Foo> like that?

Is there some other pattern I should be using instead? Should IReadOnlyFoo and IReadWriteFoo both inherit from a common base interface IFoo ?

Edit: To clarify what I am trying to do, I'm adding the actual code that I'm working with here:

public interface IOptionSelector<T>
{

    IReadOnlyCollection<T> Options { get; }
    T SelectedOption { get; }
    event EventHandler SelectedOptionChanged;
}

public interface IWriteableOptionSelector<T> : IOptionSelector<T>
{
    new ICollection<T> Options { get; }
    new T SelectedOption { get; set; }
}    

Answer 1

Here is what you should do:

public interface IOptionSelector<T>
{
    event EventHandler SelectedOptionChanged;
}
public interface IReadOnlyOptionSelector<T> : IOptionSelector<T>
{
    IReadOnlyCollection<T> Options { get; }
}
public interface IWritableOptionsSelector<T> : IOptionSelector<T>
{
    ICollection<T> Options { get; }
}

ReadOnly and Writeable are two separate concerns. When you have to use the new keyword on methods that you wrote that is a clear indication that you are dealing with separate concerns and need to rethink your design.